Swelling in the ankles, feet and legs is often caused by a build-up of fluid in these areas and is called oedema. Oedema is usually caused by standing or sitting in the same position for too long/eating too much salty food / being overweight / being pregnant / taking certain medicines such as some blood pressure medicines, contraceptive pills, antidepressants or steroids.
Oedema can also be caused by an injury such as a strain or sprain, an insect bite or sting, problems with your kidneys, liver or heart, a blood clot or an infection
Swelling in your ankles, feet or legs should go away on its own, but there are some things you can try to help :i.e. lie down and use pillows to raise the swollen area when you can, get some gentle exercise like walking to improve your blood flow, wear wide, comfortable shoes with a low heel and soft sole, wash, dry and moisturise your feet to avoid infections. Do not stand or sit for long periods of time, do not wear clothes, socks or shoes that are too tight.
If the swelling has not improved after treating it at home for a few days, or it gets worse, see a GP. Treatment for swelling or oedema that does not go away on its own will depend on the cause. It may include lifestyle changes, such as losing weight or going on a low-salt diet.